Safe electronic pyro trigger

ABSTRACT

An electronic trigger for pyro testing has a mechanical relay that is normally open. The relay is fired by electronic logic that times out two seconds after attempting to close the relay to trigger a device, such as a device coupled to explosive material. This results in the relay returning to its normally open state. By virtue of the mechanical relay being in a normally open state, no current may pass through the relay after the logic times out. A display shows status of the trigger and a count down following user activation of an enable arm switch. The countdown is stopped upon activation of the abort switch, also preventing activation of the mechanical relay.

FIELD OF THE INVENTION

The present invention relates to electronic pyro triggers, and inparticular, to a failsafe electronic pyro trigger.

BACKGROUND OF THE INVENTION

Explosive devices including blast caps are routinely pyro tested inblast cells by test engineers or technicians. When pyro testing, peopleneed a fail safe electronic trigger to protect them while working in ablast cell. When a faulty blast cap is encountered during testing, it iscrucial to know that a blasting trigger will not try to fire the capafter a count down is over, or halted by an abort command.

SUMMARY OF THE INVENTION

An electronic trigger for pyro testing has a mechanical relay that isnormally open. The relay is fired by electronic logic that times out twoseconds after attempting to close the relay to trigger a device, such asa device coupled to explosive material. This results in the relayreturning to its normally open state. By virtue of the mechanical relaybeing in a normally open state, no current may pass through the relayafter the logic times out.

In one embodiment, the electronic logic is a microprocessor. Themicroprocessor has an enable arm switch and an abort switch as inputs.The microprocessor operates software that drives a solid state relaylinked to a mechanical relay that fires a blasting cap device. Anotheroutput drives a transistor that controls a field that drives themechanical relay. A four bit output drives a display for showing a countdown following user activation of the enable arm switch. The countdownis stopped upon activation of the abort switch, also preventingactivation of the solid state relay and the field in the mechanicalrelay.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a fail safe electronic pyro triggeraccording to an embodiment of the invention.

FIG. 2 is a more detailed block diagram of the fail safe electronic pyrotrigger according to an embodiment of the invention.

FIG. 3 is a block diagram of top view of a fire box incorporating thefail safe electronic pyro trigger according to an embodiment of theinvention.

FIG. 4 is a flow chart of functions performed by the fail safeelectronic pyro trigger according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, reference is made to the accompanyingdrawings that form a part hereof, and in which is shown by way ofillustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and thatstructural, logical and electrical changes may be made without departingfrom the scope of the present invention. The following description is,therefore, not to be taken in a limited sense, and the scope of thepresent invention is defined by the appended claims.

The functions or algorithms described herein are implemented in softwareor a combination of software and human implemented procedures in oneembodiment. The software comprises computer executable instructionsstored on computer readable media such as memory or other type ofstorage devices. The term “computer readable media” is also used torepresent carrier waves on which the software is transmitted. Further,such functions correspond to modules, which are software, hardware,firmware or any combination thereof. Multiple functions are performed inone or more modules as desired, and the embodiments described are merelyexamples. The software is executed on a digital signal processor, ASIC,microprocessor, or other type of processor operating on a computersystem, such as a personal computer, server or other computer system.

A fail safe electronic trigger system is shown generally at 100 inFIG. 1. In one embodiment, system 100 has a user input 110 having afirst enable switch 112, a second enable switch 114 and an abort switch116 coupled to a controller 120. The controller may be a microprocessoror any other type of device capable of executing logic to provide one ormore output signals in response to multiple inputs. In one embodiment,the outputs are used to provide a status of the controller, including avisible countdown on a display 125 for activation of a blasting caprepresented as output 130. An output 132 to display 125 is a four bitoutput in one embodiment to drive a single character 7 segment lightemitting diode (LED) display. Many other types of outputs and displaysmay be used.

First enable switch 112 is an enable arm switch that is used toinitialize or arm the controller 120, and the second enable switch 114is an enable count switch that is used to start a countdown by thecontroller 120. Numerous other types of switches may also be used.

The controller also drives a relay 135 that is linked to a mechanicalblasting relay 140 that fires the blasting cap at 130. Relay 135 is asolid state relay in one embodiment. Blasting relay 140 is normallyopen. Another output is coupled to a current amplifier 142 that drives arelay 145 that controls a field that drives the blasting relay 140.Output 132 drives the display 125 for showing a count down followinguser activation of the enable count switch 114. The countdown is stoppedupon activation of the abort switch 116, also preventing activation ofthe solid state 135 and blasting 140 relays. A predetermined time afterthe countdown ends, activation of the solid state 135 and blasting 140relays is also prevented.

Further detail of the system 100 is shown in FIG. 2. Display 125contains both an LED character 210 and a fire lock out lamp 215, whichis on when the blasting relay 140 is prevented from firing the blastingcap. Solid state relay 135 contains an element or circuitry logicallyrepresented as a coil 220 coupled to the controller 120, and a switch225 activated by the circuitry 220. Switch 225 is coupled to a switch230 in blasting relay 140 that is directly coupled to output 130.Blasting relay 140 also contains a field generator such as an inductoror coil 235 for producing a field to activate or enable switch 230 undercontrol of relay 145 containing inductor 240 and switch 245.

FIG. 3 shows a top view of a container or fire box 310 for the system100. The fire box 310 contains the LED character 210, the fire lock outlamp 215, and switches 112, 114, and 116. It also contains a safetybreaker input 315 and blasting cap inputs 320 and 325 which are used tocouple the fire box 310 to blasting caps or other explosive orpyrotechnic devices that may be electrically activated. It may also beused for firing model rockets or other recreational devices. In furtherembodiments, the inputs 320 and 325 may be modified to activateexplosives in a different manner, such as magnetically or hydraulicallyor in any other manner desired.

FIG. 4 is a flowchart showing functions performed by the controller. Inone embodiment, the controller is a microprocessor running Parallax,Inc. Basic Stamp™ software. Other types of controller and software maybe used as is apparent to those of skill in the art.

Power to the fire box 310 is provided at 410. The controller enters intoa safe mode 415 by opening relay 145, and ensuring that relay 135 isopen. The display is initialized to display that the power is on bydisplaying a character, such as an “A” for a predetermined amount oftime, such as 0.7 seconds, then displaying blank, followed by an “A”again, followed by “0”. Any characters may be used. A loop is performed,with the display blinking “0”, waiting for the enable switch 112 to beactuated at 420. The display is then set to “E”, blanked, set to “A”,blanked again, and then stet to “F”, which blinks in a loop waiting forthe enable count switch 114 to be actuated at 425. When the enable countswitch 114 is actuated, the display displays and “E” and a “C” forpredetermined times, with predetermined delays between, and then countsdown from “9” to “0” one second at a time.

At count “0”, relay 145 is closed to provide a field to relay 140, onesecond is waited, and the relay 135 is turned on, enabling current toflow to the blast cap through relay 140. The display is also set to “B”to indicate blast. A predetermined time is then waited, 3 seconds in oneembodiment, and the controller shuts down the field through relay 145 at440 and shuts down or removes the current at 445. It then enters thesafe mode loop at 415. At any time prior to blasting, the abort switchmay be actuated at 450, resulting in immediate shut down of the field at440 and current at 445. The order of these shut downs may be varied infurther embodiments. In one embodiment, the blasting cap is fired andexplodes while the relay 135 is turned on and current is flowing to theblast cap.

A double safety is provided by the controller shutting down the field ofthe blasting relay, and shutting down the blast current applied to theblasting cap through the blasting relay. In further embodiments, thecontroller may be divided into two or more logical components, eachcoupled to separate relays to accomplish the functions. Other types ofrelays that require two inputs to trigger may be used to provide thedouble safety mechanism. One safety mechanism involves providing acontinuous signal that allows operation of the blasting relay. In oneembodiment, this is the relay that provides current to the coil 235 tocreate a field and close the switch. A further safety mechanism is therelay 135 that must be activated to provide current through the blastingrelay 140 to the blasting cap at output 130. In further embodiments,other types of safety mechanisms are used to enable a switch, and toprovide blasting current to the enabled switch. In yet a furtherembodiment, a short in the blasting cap current loop is detected,causing the controller to shift into the fail safe mode until the firingsequence is restarted. This detection is performed with a circuitbreaker, such as a five ampere circuit breaker in one embodiment.

1. An electronic trigger comprising: a first relay having a triggeroutput; a second relay coupled to the first relay that selectivelyenables the first relay; and a controller coupled to the first relay andto the second relay, wherein the controller provides an enable signal tothe second relay to enable the first relay, and provides a signal to thefirst relay for providing the trigger output when the first relay isenabled.
 2. The electronic trigger of claim 1 wherein the first relaycomprises a normally open mechanical switch.
 3. The electronic triggerof claim 1 wherein the controller is coupled to user inputs.
 4. Theelectronic trigger of claim 3 wherein the user inputs comprise an enablearm switch, an enable count switch and an abort switch.
 5. Theelectronic trigger of claim 4 wherein the enable arm switch causes thecontroller to enter a safe mode loop.
 6. The electronic trigger of claim5 wherein the enable count switch causes the controller to count downfrom a predetermined number.
 7. The electronic trigger of claim 1 andfurther comprising a display coupled to the controller.
 8. Theelectronic trigger of claim 1 and further comprising a current drivercoupled between the controller and the second relay for providing acurrent to enable the first relay.
 9. The electronic trigger of claim 1and further comprising a third relay coupled between the controller andthe first relay for switching current to the first relay under controlof the controller, wherein the current becomes the output signal of thefirst relay.
 10. An electronic trigger comprising: a blast relay havingan output for triggering a blast cap; means for activating the blastrelay; and means for providing a signal to the blast relay for providingthe output for triggering the blast cap.
 11. The electronic trigger ofclaim 10 and further comprising means for displaying the status of thecontroller.
 12. An electronic trigger comprising: a set of user inputscomprising an enable arm switch, an enable count switch and an abortswitch; a first relay having an output for triggering a blast cap,wherein the first relay has a switch and a field generator; a secondrelay coupled to the first relay for enabling the field generator toactivate the first relay switch; a third relay coupled to the firstrelay for providing a signal that is passed through the first relayswitch as the output signal when the first relay switch is activated; adisplay; and a controller that receives the user inputs, provides statusand countdown signals to the display, and controls the second and thirdrelays.
 13. A method for controlling an output signal provided to adevice, the method comprising: enabling a relay; providing a signal tothe relay that is provided as the output signal when the relay isenabled; disabling the relay after a predetermined time; and removingthe signal to the relay.
 14. The method of claim 13 wherein the relay isdisabled prior to stopping providing the signal to the relay.
 15. Themethod of claim 13 wherein the predetermined time is approximately threeseconds.
 16. The method of claim 13 and further comprising counting downby seconds from a predetermined number of seconds prior to enabling therelay.
 17. An electronically implemented method for controlling anoutput signal provided to a device, the method comprising: entering asafe mode loop; entering an enable loop; entering a countdown loop;enabling a relay after a predetermined time in the countdown loop;providing a signal to the relay that is provided as the output signalwhen the relay is enabled; disabling the relay after a predeterminedamount of time; and removing the signal to the relay.
 18. The method ofclaim 17 and further comprising providing status signals to a display.19. The method of claim 17 wherein the enable loop is entered afterdetecting actuation of an enable arm switch.
 20. The method of claim 19wherein the count down loop is entered following the enable loop, and inresponse to detection of actuation of an enable count switch.
 21. Themethod of claim 19 wherein the relay is disabled and the signal to therelay is stopped upon detection of actuation of an abort switch.
 22. Themethod of claim 16 and further comprising firing a blasting while therelay is enabled and the signal is provided to the relay.
 23. A systemfor controlling an output signal provided to an explosive device, themethod comprising: means for enabling a relay; means for providing asignal to the relay that is provided as the output signal when the relayis enabled; means for disabling the relay after a predetermined time;and means for removing the signal to the relay.